Add description for disabling crash reporter with environment variables or ini file

It is found in https://github.com/mozilla-japan/enterprise/blob/67fc851bdec0785e78451cdabbc14a8a9448b87e/FAQ.md#設定方法-9.
But this repository does not describe how to disable without MCD or fainstall.ini. 

Should we describe how to disable not rely on MCD or fainstall.ini?
- Using Windows registry
- Using macOS's app settings
- Using ini file settings per user in Linux
